Meta-programming in Ruby and JavaScript

Recently, I have been working with writing a ruby gem, Yoolk API Gem. What is really interesting for me is I do some meta programming and object-oriented programming in Ruby which I have never experienced before. A few month later, there is a requirement that my team needs to write in JavaScript, but I don't want to touch JavaScript really much. Therefore, my team member took over this task. Whenever I write code in Ruby, I just try to think how to do it in JavaScript as well. Several things that came up to my mind with some from my team member:

1. Defer class from a variable.

// JavaScript
var klass = "Person";
p = new window[klass]; //class without namespace
p = new yoolk[klass]; //class with namespace

# Ruby
klass = "Person"
p = Object.const_get(klass).new #class without namespace
p = Yoolk.const_get(klass).new #class with namespace

2. Access class method from instance object

// JavaScript
var p = new Person();
p.constructor.getCount();

#Ruby
p = Person.new
p.class.count

3. Define method of an object

//JavaScript
var p = new Person();
p.hello = function() {
  alert('hello');
};

//Ruby
p = Person.new
def p.hello
  puts "hello"
end

4. Define class methods

//JavaScript
Person.hello = function() {
  alert('hello');
};

//Ruby
def Person.hello
  puts "hello"
end